#include <iostream>

using namespace std;

int main()
{
	double x;
	cin >> x;

	double l = -10000, r = 10000;
	while(r - l > 1e-8)
	{
		double mid = (l + r) / 2;
		if (mid * mid * mid >= x) r = mid;
		else l = mid;
	}
	
	printf("%lf\n",l);
	
	return 0;
}